Internal tide

Internal waves at a tidal frequency generated as surface tides move stratified water up and down a slope

Internal tides are generated as the surface tides move stratified water up and down sloping topography, which produces a wave in the ocean interior. So internal tides are internal waves at a tidal frequency. The other major source of internal waves is the wind which produces internal waves near the inertial frequency. When a small water parcel is displaced from its equilibrium position, it will return either downwards due to gravity or upwards due to buoyancy. The water parcel will overshoot its original equilibrium position and this disturbance will set off an internal gravity wave. Munk (1981) notes, "Gravity waves in the ocean's interior are as common as waves at the sea surface-perhaps even more so, for no one has ever reported an interior calm."
[1]

Figure 1: Water parcels in the whole water column move together with the surface tide (top), while shallow and deep waters move in opposite directions in an internal tide (bottom). The surface displacement and interface displacement are the same for a surface wave (top), while for an internal wave the surface displacements are very small, while the interface displacements are large (bottom). This figure is a modified version of one appearing in Gill (1982). [2]

The surface tide propagates as a wave, in which water parcels in the whole water column oscillate in the same direction at a given phase (i.e., in the trough or at the crest, Fig. 1, top). At the simplest level, an internal wave can be thought of as an interfacial wave (Fig. 1, bottom). If there are two levels in the ocean, such as a warm surface layer and cold deep layer separated by a thermocline,then motions on the interface are possible. The interface movement is large compared to surface movement. The restoring force for internal waves and tides is still gravity but its effect is reduced because the densities of the 2 layers are relatively similar compared to the large density difference at the air-sea interface. Thus larger displacements are possible inside the ocean than at the sea surface.

Tides occur mainly at diurnal and semidiurnal periods. The principal lunar semidiurnal constituent is known as M2 and generally has the largest amplitudes. (See external links for more information.)

The largest internal tides are generated at steep, midocean topography such as the Hawaiian Ridge, Tahiti, the Macquarie Ridge, and submarine ridges in the Luzon Strait.
[3]
Continental slopes such as the Australian North West Shelf also generate large internal tides.
[4]
These internal tide may propagate onshore and dissipate much like surface waves. Or internal tides may propagate away from the topography into the open ocean. For tall, steep, midocean topography, such as the Hawaiian Ridge, it is estimated that about 85% of the energy in the internal tide propagates away into the deep ocean with about 15% of its energy being lost within about 50 km of the generation site. The lost energy contributes to turbulence and mixing near the generation sites.
[5][6]
It is not clear where the energy that leaves the generation site is dissipated, but there are 3 possible processes: 1) the internal tides scatter and/or break at distant midocean topography, 2) interactions with other internal waves remove energy from the internal tide, or 3) the internal tides shoal and break on continental shelves.

Figure 2: The internal tide sea surface elevation that is in phase with the surface tide (i.e., crests occur in a certain spot at a certain time that are both the same relative to the surface tide) can be detected by satellite (top). (The satellite track is repeated about every 10 days and so M2 tidal signals are shifted to longer periods due to aliasing.) The longest internal tide wavelengths are about 150 km near Hawaii and the next longest waves are about 75 km long. The surface displacements due to the internal tide are plotted as wiggly red lines with amplitudes plotted perpendicular to the satellite groundtracks (black lines). Figure is adapted from Johnston et al. (2003).

Briscoe (1975)noted that “We cannot yet answer satisfactorily the questions: ‘where does the internal wave energy come from, where does it go, and what happens to it along the way?’”
[7]
Although technological advances in instrumentation and modeling have produced greater knowledge of internal tide and near-inertial wave generation, Garrett and Kunze (2007) observed 33 years later that “The fate of the radiated [large-scale internal tides] is still uncertain. They may scatter into [smaller scale waves] on further encounter with islands[8][9]
or the rough seafloor
[10]
, or transfer their energy to smaller-scale internal waves in the ocean interior
[11]
” or “break on distant continental slopes
[12]”.
[13]
It is now known that most of the internal tide energy generated at tall, steep midocean topography radiates away as large-scale internal waves. This radiated internal tide energy is one of the main sources of energy into the deep ocean, roughly half of the wind energy input
.[14] Broader interest in internal tides is spurred by their impact on the magnitude and spatial inhomogeneity of mixing, which in turn has first order effect on the meridional overturning circulation
[3][14]
.[15]

The internal tidal energy in one tidal period going through an area perpendicular to the direction of propagation is called the energy flux and is measured in Watts/m2{\displaystyle ^{2}}. The energy flux at one point can be summed over depth- this is the depth-integrated energy flux and is measured in Watts/m. The Hawaiian Ridge produces depth-integrated energy fluxes as large as 10 kW/m. The longest wavelength waves are the fastest and thus carry most of the energy flux. Near Hawaii, the typical wavelength of the longest internal tide is about 150 km while the next longest is about 75 km. These waves are called mode 1 and mode 2, respectively. Although Fig. 1 shows there is no sea surface expression of the internal tide, there actually is a displacement of a few centimeters. These sea surface expressions of the internal tide at different wavelengths can be detected with the Topex/Poseidon or Jason-1 satellites (Fig. 2).
[9]
Near 15 N, 175 W on the Line Islands Ridge, the mode-1 internal tides scatter off the topography, possibly creating turbulence and mixing, and producing smaller wavelength mode 2 internal tides.
[9]

The inescapable conclusion is that energy is lost from the surface tide to the internal tide at midocean topography and continental shelves, but the energy in the internal tide is not necessarily lost in the same place. Internal tides may propagate thousands of kilometers or more before breaking and mixing the abyssal ocean.

The importance of internal tides and internal waves in general relates to their breaking, energy dissipation, and mixing of the deep ocean. If there were no mixing in the ocean, the deep ocean would be a cold stagnant pool with a thin warm surface layer.
[16]
While the meridional overturning circulation (also referred to as the thermohaline circulation) redistributes about 2 PW of heat from the tropics to polar regions, the energy source for this flow is the interior mixing which is comparatively much smaller- about 2 TW.
[14]
Sandstrom (1908) showed a fluid which is both heated and cooled at its surface cannot develop a deep overturning circulation.
[17]
Most global models have incorporated uniform mixing throughout the ocean because they do not include or resolve internal tidal flows.

However, models are now beginning to include spatially variable mixing related to internal tides and the rough topography where they are generated and distant topography where they may break. Wunsch and Ferrari (2004) describe the global impact of spatially inhomogeneous mixing near midocean topography: “A number of lines of evidence, none complete, suggest that the oceanic general circulation, far from being a
heat engine, is almost wholly governed by the forcing of the wind field and secondarily by deep water tides... The now
inescapable conclusion that over most of the ocean significant ‘vertical’ mixing is confined to topographically complex boundary areas implies a potentially radically different interior circulation than is possible with uniform mixing.
Whether ocean circulation models... neither explicitly accounting for the energy input into the system nor providing
for spatial variability in the mixing, have any physical relevance under changed climate conditions is at issue.” There is a limited understanding of “the sources controlling the internal wave energy in the ocean and
the rate at which it is dissipated” and are only now developing some “parameterizations of the mixing generated by
the interaction of internal waves, mesoscale eddies, high-frequency barotropic fluctuations, and other motions over
sloping topography.”

Figure 3: The internal tide produces large vertical differences in temperature at the research pier at the Scripps Institution of Oceanography. The black line shows the surface tide elevation relative to mean lower low water (MLLW). Figure provided by Eric Terrill, Scripps Institution of Oceanography with funding from the U.S. Office of Naval Research

Internal tides may also dissipate on continental slopes and shelves
[12]
or even reach within 100 m of the beach (Fig. 3). Internal tides bring pulses of cold water shoreward and produce large vertical temperature differences. When surface waves break, the cold water is mixed upwards, making the water cold for surfers, swimmers, and other beachgoers. Surface waters in the surf zone can change by about 10 °C in about an hour.

Internal tides generated by tidal semidiurnal currents impinging on steep submarine ridges in island passages, ex: Mona Passage, or near the shelf edge, can enhance turbulent dissipation and internal mixing near the generation site. The development of Kelvin-Helmholtz instability during the breaking of the internal tide can explain the formation of high diffusivity patches that generate a vertical flux of nitrate (NO3−) into the photic zone and can sustain new production locally.
[18][19]
Another mechanism for higher nitrate flux at spring tides results from pulses of strong turbulent dissipation associated with high frequency internal soliton packets.
[20]
Some internal soliton packets are the result of the nonlinear evolution of the internal tide.

1.
Tide
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Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. Some shorelines experience a semi-diurnal tide—two nearly equal high and low tides each day, other locations experience a diurnal tide—only one high and low tide each day. A mixed tide—two uneven tides a day, or one high, Tides vary on timescales ranging from hours to years due to a number of factors. To make accurate records, tide gauges at fixed stations measure water level over time, gauges ignore variations caused by waves with periods shorter than minutes. These data are compared to the level usually called mean sea level. Tidal phenomena are not limited to the oceans, but can occur in other systems whenever a gravitational field varies in time. For example, the part of the Earth is affected by tides. Tide changes proceed via the following stages, Sea level rises over several hours, covering the intertidal zone, the water rises to its highest level, reaching high tide. Sea level falls over several hours, revealing the intertidal zone, the water stops falling, reaching low tide. Oscillating currents produced by tides are known as tidal streams, the moment that the tidal current ceases is called slack water or slack tide. The tide then reverses direction and is said to be turning, slack water usually occurs near high water and low water. But there are locations where the moments of slack tide differ significantly from those of high, Tides are commonly semi-diurnal, or diurnal. The two high waters on a day are typically not the same height, these are the higher high water. Similarly, the two low waters each day are the low water and the lower low water. The daily inequality is not consistent and is small when the Moon is over the equator. From the highest level to the lowest, Highest Astronomical Tide – The highest tide which can be predicted to occur, note that meteorological conditions may add extra height to the HAT. Mean High Water Springs – The average of the two high tides on the days of spring tides, mean High Water Neaps – The average of the two high tides on the days of neap tides. Mean Sea Level – This is the sea level

2.
TOPEX/Poseidon
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Launched on August 10,1992, TOPEX/Poseidon was a joint satellite mission between NASA, the U. S. space agency, and CNES, the French space agency, to map ocean surface topography. The first major oceanographic research vessel to sail into space, TOPEX/Poseidon helped revolutionize oceanography by proving the value of satellite ocean observations, oceanographer Walter Munk described TOPEX/Poseidon as the most successful ocean experiment of all time. A malfunction ended normal satellite operations in January 2006, before TOPEX/Poseidon, scientists had only a brief glimpse of Earths ocean as a whole from the pioneering, but short-lived Seasat satellite. TOPEX/Poseidon radar altimeter provided the first continuous global coverage of the topography of the oceans. From orbit 1,330 kilometers above Earth, TOPEX/Poseidon provided measurements of the height of 95 percent of the ice-free ocean to an accuracy of 3.3 centimeters. The satellites measurements of the hills and valleys of the sea led to a fundamental new understanding of ocean circulation. The missions most important achievement was to determine the patterns of ocean circulation - how heat stored in the moves from one place to another. Since the ocean holds most of the Earths heat from the Sun, TOPEX/Poseidon made it possible for the first time to compare computer models of ocean circulation with actual global observations and use the data to improve climate predictions. While a three-year prime mission was planned, TOPEX/Poseidon delivered more than 10 years of data from orbit, lift-off from Kourou in French Guiana took place on 1992-08-10. At lift-off the mass of the satellite was 2,402 kilograms, the mission was named after the ocean TOPography EXperiment and the Greek god of the ocean Poseidon. In October 2005 after more than 62,000 orbits, TOPEX/Poseidon stopped providing science data after a momentum wheel malfunctioned, tOPEX/Poseidons follow-on mission, Jason-1, was launched in 2001 to continue the ongoing measurements of sea surface topography. The record of sea surface height begun by TOPEX/Poseidon and Jason-1 continues into the future with the Ocean Surface Topography Mission on the Jason-2 satellite. Planning for a Jason-3 mission is now underway, TOPEX/Poseidon flew two onboard altimeters sharing the same antenna, but only one altimeter was operated at any time, with TOPEX given preference. TOPEX, The NASA-built Nadir pointing Radar Altimeter using C band, Poseidon, The CNES-built solid state Nadir pointing Radar Altimeter using Ku band. In addition to the altimeters, the TOPEX Microwave Radiometer operating at 18,21, the satellite was also equipped with instruments to accurately pinpoint its location. Precise orbit determination is crucial because errors in locating the spacecraft would distort the sea level measurement calculated from the altimeter readings, three independent tracking systems determined the position of the spacecraft. The first, the NASA laser retroreflector array reflected laser beams from a network of 10 to 15 ground-based laser ranging stations under clear skies, the second, for all-weather, global tracking, was provided by the CNES Doppler Orbitography and Radiopositioning Integrated by Satellite tracking system receiver. This device uses microwave doppler techniques to track the spacecraft, DORIS consists of an on-board receiver and a global network of 40 to 50 ground-based transmitting stations. S Air Forces GPS constellation of Earth orbiting satellites

3.
Scripps Institution of Oceanography
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Hundreds of ocean and Earth scientists conduct research with the aid of oceanographic research vessels and shorebased laboratories. Its Old Scripps Building is a U. S. National Historic Landmark, SIO is a department of the University of California, San Diego. The public explorations center of the institution is the Birch Aquarium at Scripps, since becoming part of the University of California in 1912, the institution has expanded its scope to include studies of the physics, chemistry, geology, biology, and climate of Earth. Dr. Margaret Leinen took office as Vice Chancellor for Marine Sciences, Director of Scripps Institution of Oceanography, Scripps publishes explorations now, an e-magazine of ocean and earth science. To seek, teach, and communicate scientific understanding of the oceans, atmosphere, Earth, and other planets for the benefit of society, Scripps Institution of Oceanography was founded in 1903 as the Marine Biological Association of San Diego, an independent biological research laboratory. It was proposed and incorporated by a committee of the San Diego Chamber of Commerce, led by local activist and they fully funded the institution for its first decade. It began institutional life in the boathouse of the Hotel del Coronado located on San Diego Bay and it re-located in 1905 to the La Jolla area on the head above La Jolla Cove, and finally in 1907 to its present location. In 1912 Scripps became part of the University of California and was renamed the Scripps Institution for Biological Research, the name was changed to Scripps Institution of Oceanography in October 1925. The Old Scripps Building, designed by Irving Gill, was declared a National Historic Landmark in 1982, architect Barton Myers designed the current Scripps Building. The institutions research programs encompass biological, physical, chemical, geological, Scripps also studies the interaction of the oceans with both the atmospheric climate and environmental concerns on terra firma. Related to this research, Scripps offers undergraduate and graduate degrees, today, the Scripps staff of 1,300 includes approximately 235 faculty,180 other scientists and some 300 graduate students, with an annual budget of more than $195 million. The institution operates a fleet of three research vessels and the research platform R/P FLIP for oceanographic research. – RV Ellen B. Scripps 1966–1992 – RV Thomas Washington 1969–2014 – RV Melville 1973–, in 2014, the institution and its Keeling Curve measurement of atmospheric carbon dioxide levels were featured as a plot point in an episode of HBOs The Newsroom. In 2008, Scripps Institution of Oceanography was the subject of a category on the TV game show Jeopardy, Scripps has been a story element in numerous fictional works. Array Network Facility The Scripps Research Institute, a neighboring, woods Hole Oceanographic Institution, a similar research facility on the east coast of the USA. Monterey Bay Aquarium Research Institute, a private, non-profit oceanographic research center in Moss Landing, Scripps Institution of Oceanography, First Fifty Years Helen Raitt and Beatrice Moulton. Los Angeles, W. Ritchie Press,1967, Scripps Institution of Oceanography, Probing the Oceans,1936 to 1976 Elizabeth Noble Shor

4.
Texas A&M University
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Texas A&M University is a coeducational public research university in College Station, Texas, United States. It is a university and is a member of the Texas A&M University System. The systems endowment ranks in the top 10 in the nation, Texas A&Ms student body is the largest in Texas and one of the largest in the United States. In 2001, Texas A&M was inducted as a member of the prestigious Association of American Universities, the schools students, alumni–over 450,000 strong–and sports teams are known as Aggies. The Texas A&M Aggies athletes currently compete in 18 varsity sports as a member of the Southeastern Conference, originally, the college taught no classes in agriculture, instead concentrating on classical studies, languages, literature, and applied mathematics. After four years, students could attain degrees in agriculture, civil and mechanical engineering. Under the leadership of President James Earl Rudder in the 1960s, A&M desegregated, became coeducational, to reflect the institutions expanded roles and academic offerings, the Texas Legislature renamed the school to Texas A&M University in 1963. The letters A&M, originally short for Agricultural and Mechanical, are retained only as a link to the universitys past, the main campus is one of the largest in the United States, spanning 5,200 acres, and is home to the George Bush Presidential Library. About one-fifth of the student body lives on campus, Texas A&M has over 1,000 officially recognized student organizations. Many students also observe the traditions, which daily life, as well as special occasions. Working with agencies such as the Texas AgriLife Research and Texas AgriLife Extension Service, the university offers degrees in over 150 courses of study through ten colleges and houses 18 research institutes. As a Senior Military College, Texas A&M is one of six American public universities with a full-time, the U. S. Congress laid the groundwork for the establishment of Texas A&M in 1862 with the adoption of the Morrill Act. To promote the liberal and practical education of the classes in the several pursuits. In 1871, the Texas Legislature used these funds to establish the states first public institution of higher education, Brazos County donated 2,416 acres near Bryan, Texas, for the schools campus. Enrollment began on October 2,1876, six students enrolled on the first day, and classes officially began on October 4,1876, with six faculty members. During the first semester, enrollment increased to 48 students, admission was limited to white males, and all students were required to participate in the Corps of Cadets and receive military training. Although traditional Texas A&M University Corps of Cadets campusologies indicate 40 students began classes on October 4,1876, enrollment climbed to 258 students before declining to 108 students in 1883, the year the University of Texas opened in Austin, Texas. In the late 1880s, many Texas residents saw no need for two colleges in Texas and clamored for an end of Texas A. M. C

5.
Wind wave
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In fluid dynamics, wind waves, or wind-generated waves, are surface waves that occur on the free surface of bodies of water. They result from the wind blowing over an area of fluid surface, Waves in the oceans can travel thousands of miles before reaching land. Wind waves on Earth range in size from small ripples, to waves over 100 ft high, when directly generated and affected by local winds, a wind wave system is called a wind sea. After the wind ceases to blow, wind waves are called swells, more generally, a swell consists of wind-generated waves that are not significantly affected by the local wind at that time. They have been generated elsewhere or some time ago, wind waves in the ocean are called ocean surface waves. Wind waves have an amount of randomness, subsequent waves differ in height, duration. The key statistics of wind waves in evolving sea states can be predicted with wind wave models, although waves are usually considered in the water seas of Earth, the hydrocarbon seas of Titan may also have wind-driven waves. The great majority of large breakers seen at a result from distant winds. Water depth All of these work together to determine the size of wind waves. Further exposure to that wind could only cause a dissipation of energy due to the breaking of wave tops. Waves in an area typically have a range of heights. For weather reporting and for analysis of wind wave statistics. This figure represents an average height of the highest one-third of the waves in a time period. The significant wave height is also the value a trained observer would estimate from visual observation of a sea state, given the variability of wave height, the largest individual waves are likely to be somewhat less than twice the reported significant wave height for a particular day or storm. Wave formation on a flat water surface by wind is started by a random distribution of normal pressure of turbulent wind flow over the water. This pressure fluctuation produces normal and tangential stresses in the surface water and it is assumed that, The water is originally at rest. There is a distribution of normal pressure to the water surface from the turbulent wind. Correlations between air and water motions are neglected, the second mechanism involves wind shear forces on the water surface

6.
Physical oceanography
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Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters. Physical oceanography is one of several sub-domains into which oceanography is divided, others include biological, chemical and geological oceanography. Physical oceanography may be subdivided into descriptive and dynamical physical oceanography, descriptive physical oceanography seeks to research the ocean through observations and complex numerical models, which describe the fluid motions as precise as possible. Dynamical physical oceanography focuses primarily upon the processes that govern the motion of fluids with emphasis upon theoretical research and these are part of the large field of Geophysical Fluid Dynamics that is shared together with meteorology. The fundamental role of the oceans in shaping Earth is acknowledged by ecologists, geologists, meteorologists, climatologists, an Earth without oceans would truly be unrecognizable. Roughly 97% of the water is in its oceans. The tremendous heat capacity of the oceans moderates the planets climate, the oceans influence extends even to the composition of volcanic rocks through seafloor metamorphism, as well as to that of volcanic gases and magmas created at subduction zones. Though this apparent discrepancy is great, for land and sea, the respective extremes such as mountains and trenches are rare. Because the vast majority of the oceans volume is deep water. The same percentage falls in a salinity range between 34–35 ppt, there is still quite a bit of variation, however. Surface temperatures can range from below freezing near the poles to 35 °C in restricted tropical seas, in terms of temperature, the oceans layers are highly latitude-dependent, the thermocline is pronounced in the tropics, but nonexistent in polar waters. The halocline usually lies near the surface, where evaporation raises salinity in the tropics and these variations of salinity and temperature with depth change the density of the seawater, creating the pycnocline. Energy for the ocean circulation comes from solar radiation and gravitational energy from the sun, perhaps three quarters of this heat is carried in the atmosphere, the rest is carried in the ocean. The atmosphere is heated from below, which leads to convection, by contrast the ocean is heated from above, which tends to suppress convection. Instead ocean deep water is formed in regions where cold salty waters sink in fairly restricted areas. This is the beginning of the thermohaline circulation, oceanic currents are largely driven by the surface wind stress, hence the large-scale atmospheric circulation is important to understanding the ocean circulation. The Hadley circulation leads to Easterly winds in the tropics and Westerlies in mid-latitudes and this leads to slow equatorward flow throughout most of a subtropical ocean basin. The return flow occurs in an intense, narrow, poleward western boundary current, like the atmosphere, the ocean is far wider than it is deep, and hence horizontal motion is in general much faster than vertical motion

7.
Aliasing
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In signal processing and related disciplines, aliasing is an effect that causes different signals to become indistinguishable when sampled. It also refers to the distortion or artifact that results when the signal reconstructed from samples is different from the continuous signal. Aliasing can occur in signals sampled in time, for digital audio. Aliasing can also occur in spatially sampled signals, for instance moiré patterns in digital images, aliasing in spatially sampled signals is called spatial aliasing. Aliasing is generally avoided by applying low pass filters- anti-aliasing filters to the signal before sampling. When a digital image is viewed, a reconstruction is performed by a display or printer device, and by the eyes and the brain. If the image data is processed in some ways during sampling or reconstruction, the image will differ from the original image. An example of aliasing is the moiré pattern observed in a poorly pixelized image of a brick wall. Spatial anti-aliasing techniques avoid such poor pixelizations, aliasing can be caused either by the sampling stage or the reconstruction stage, these may be distinguished by calling sampling aliasing prealiasing and reconstruction aliasing postaliasing. Temporal aliasing is a concern in the sampling of video. Music, for instance, may contain components that are inaudible to humans. If a piece of music is sampled at 32000 samples per second, to prevent this an anti-aliasing filter is used to remove components above the Nyquist frequency prior to sampling. In video or cinematography, temporal aliasing results from the frame rate. Aliasing has changed its apparent frequency of rotation, a reversal of direction can be described as a negative frequency. Like the video camera, most sampling schemes are periodic, that is, digital cameras provide a certain number of samples per degree or per radian, or samples per mm in the focal plane of the camera. Audio signals are sampled with a converter, which produces a constant number of samples per second. Some of the most dramatic and subtle examples of aliasing occur when the signal being sampled also has periodic content, actual signals have finite duration and their frequency content, as defined by the Fourier transform, has no upper bound. Some amount of aliasing always occurs when such functions are sampled, functions whose frequency content is bounded have infinite duration

8.
Jason-1
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The lineage of the name begins with the JASO1 meeting in Toulouse, France to study the problems of assimilating altimeter data in models. Jason as an acronym also stands for Joint Altimetry Satellite Oceanography Network, additionally it is used to reference the mythical quest for knowledge of Jason and the Argonauts. It is the successor to the TOPEX/Poseidon mission, which measured ocean surface topography from 1992 through 2005, like its predecessor, Jason-1 is a joint project between the NASA and CNES space agencies. Jason-1s successor, the Ocean Surface Topography Mission on the Jason-2 satellite, was launched in June 2008 and these satellites provide a unique global view of the oceans that is impossible to acquire using traditional ship-based sampling. As did TOPEX/Poseidon, Jason-1 uses an altimeter to measure the hills and these measurements of sea surface topography allow scientists to calculate the speed and direction of ocean currents and monitor global ocean circulation. The global ocean is Earths primary storehouse of solar energy, Jason-1s measurements of sea surface height reveal where this heat is stored, how it moves around Earth by ocean currents, and how these processes affect weather and climate. Jason-1 was launched on December 7,2001 from Californias Vandenberg Air Force Base aboard a Delta II rocket, during the first months Jason-1 shared an almost identical orbit to TOPEX/Poseidon, which allowed for cross calibration. At the end of period, the older satellite was moved to a new orbit midway between each Jason ground track. Jason has a cycle of 10 days. On 16 March 2002, Jason-1 experienced a sudden attitude upset, soon after this incident, two new small pieces of space debris were observed in orbits slightly lower than Jason-1s, and spectroscopic analysis eventually proved them to have originated from Jason-1. In 2011, it was determined that the pieces of debris had most likely been ejected from Jason-1 by an unidentified, small high-speed particle hitting one of the spacecrafts solar panels. Orbit maneuvers in 2009 put the Jason-1 satellite on the side of Earth from the Jason-2 satellite. Jason-1 now flies over the region of the ocean that Jason-2 flew over five days earlier. Its ground tracks fall midway between those of Jason-2, which are about 315 kilometers apart at the equator and this interleaved tandem mission provides twice the number of measurements of the oceans surface, bringing smaller features such as ocean eddies into view. The tandem mission also helps pave the way for a future ocean altimeter mission that would much more detailed data with its single instrument than the two Jason satellites now do together. The program is named after the Greek mythological hero Jason, Jason-1 has five 5 instruments, Poseidon 2 - Nadir pointing Radar Altimeter using C band and Ku band for measuring height above sea surface. Jason Microwave Radiometer - measures water vapor along altimeter path to correct for pulse delay DORIS for orbit determination to within 10 cm or less, the Jason-1 satellite, its altimeter instrument and a position-tracking antenna were built in France. The radiometer, Global Positioning System receiver and laser retroreflector array were built in the United States, TOPEX/Poseidon and Jason-1 have led to major advances in the science of physical oceanography and in climate studies

9.
Office of Naval Research
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It is headquartered in the Ballston neighborhood of Arlington, Virginia. ONR reports to the U. S. Secretary of the Navy through the Assistant Secretary of the Navy for Research, Development and Acquisition. The Chief of Naval Research is Rear Admiral Mathias W. ONR executes its mission through science and technology departments, corporate programs, the Naval Research Laboratory, the ONR Global office. In 2007, a Naval S&T Strategic Plan was developed to describe how ONR will enable the future operational concepts of the Navy and this plan was updated in 2009 and 2011. More than 50 researchers have won a Nobel Prize for their ONR-funded work, continuous investment in new and innovative technology enables ONR to build and maintain the world’s most capable Navy. Its focus is long term, yet it is responsive to near-term Naval needs. The six departments support efforts span from combating terrorism to oceanography, NRL is the corporate research laboratory for the Navy and Marine Corps and conducts a broad program of scientific research, technology and advanced development. A few of the Laboratorys current specialties include plasma physics, space physics, materials science, the U. S. Office of Naval Research Global provides worldwide science & technology-based solutions to current and future Naval challenges. ONR Global combines the expertise of over 40 scientists, technologists, oNRs investments have enabled many firsts, including the launch of the first U. S. Others include, The ONR has also sponsored symposia such as the Symposium on Principles of Self-Organization at Allerton Park in 1960, Office of Naval Research Homepage Naval Research Laboratory Homepage Naval S&T Strategic Plan

10.
Internal wave
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Internal waves are gravity waves that oscillate within a fluid medium, rather than on its surface. To exist, the fluid must be stratified, the density must decrease continuously or discontinuously with depth/height due to changes, for example, If the density changes continuously, the waves can propagate vertically as well as horizontally through the fluid. Internal waves, also called gravity waves, go by many other names depending upon the fluid stratification, generation mechanism, amplitude. If propagating horizontally along an interface where the density decreases with height. If the interfacial waves are large amplitude they are called solitary waves or internal solitons. If moving vertically through the atmosphere where substantial changes in air density influences their dynamics, If generated by flow over topography, they are called Lee waves or mountain waves. If the mountain waves break aloft, they can result in strong winds at the ground known as Chinook winds or Foehn winds. If generated in the ocean by tidal flow over submarine ridges or the continental shelf, If they evolve slowly compared to the Earths rotational frequency so that their dynamics are influenced by the Coriolis effect, they are called inertia gravity waves or, simply, inertial waves. Internal waves are usually distinguished from Rossby waves, which are influenced by the change of Coriolis frequency with latitude. An internal wave can readily be observed in the kitchen by slowly tilting back, clouds that reveal internal waves launched by flow over hills are called lenticular clouds because of their lens-like appearance. Less dramatically, a train of waves can be visualized by rippled cloud patterns described as herringbone sky or mackerel sky. The outflow of air from a thunderstorm can launch large amplitude internal solitary waves at an atmospheric inversion. In northern Australia, these result in Morning Glory clouds, used by some daredevils to glide along like a surfer riding an ocean wave, satellites over Australia and elsewhere reveal these waves can span many hundreds of kilometers. According to Archimedes principle, the weight of an object is reduced by the weight of fluid it displaces. This holds for a parcel of density ρ surrounded by an ambient fluid of density ρ0. Its weight per volume is g, in which g is the acceleration of gravity. Dividing by a density, ρ00, gives the definition of the reduced gravity. Because water is more dense than air, the displacement of water by air from a surface gravity wave feels nearly the full force of gravity

11.
Nitrate
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Nitrate is a polyatomic ion with the molecular formula NO−3 and a molecular mass of 62.0049 g/mol. Nitrates also describe the functional group RONO2. These nitrate esters are a class of explosives. The anion is the base of nitric acid, consisting of one central nitrogen atom surrounded by three identically bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a charge of −1. This arrangement is used as an example of resonance. Like the isoelectronic carbonate ion, the ion can be represented by resonance structures. A common example of a nitrate salt is potassium nitrate. A rich source of nitrate in the human body comes from diets rich in leafy green foods, such as spinach. NO3- is the active component within beetroot juice and other vegetables. Nitrite and water are converted in the body to nitric oxide, nitrate salts are found naturally on earth as large deposits, particularly of nitratine, a major source of sodium nitrate. Nitrates are found in man-made fertilizers, as a byproduct of lightning strikes in earths nitrogen-oxygen rich atmosphere, nitric acid is produced when nitrogen dioxide reacts with water vapor. Nitrates are mainly produced for use as fertilizers in agriculture because of their solubility and biodegradability. The main nitrate fertilizers are ammonium, sodium, potassium, several million kilograms are produced annually for this purpose. The second major application of nitrates is as oxidizing agents, most notably in explosives where the oxidation of carbon compounds liberates large volumes of gases. Sodium nitrate is used to air bubbles from molten glass. Mixtures of the salt are used to harden some metals. Explosives and table tennis balls are made from celluloid, although nitrites are the nitrogen compound chiefly used in meat curing, nitrates are used in certain specialty curing processes where a long release of nitrite from parent nitrate stores is needed

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the …

Image: Bay of Fundy High Tide

In Maine (U.S.) low tide occurs roughly at moonrise and high tide with a high moon, corresponding to the simple gravity model of two tidal bulges; at most places however, moon and tides have a phase shift.

Jason-1 is a satellite oceanography mission to monitor global ocean circulation, study the ties between the ocean and …

Artist's interpretation of the Jason-1 satellite

Although the 1993–2005 Topex/Poseidon satellite (on the left) measured an average annual Global Mean Sea Level rise of 3.1 mm/year, Jason-1 is measuring only 2.3 mm/year GMSL rise, and the Envisat satellite (2002–2012) is measuring just 0.5 mm/year GMSL rise. In this graph, the vertical scale represents globally averaged mean sea level. Seasonal variations in sea level have been removed to show the underlying trend. Image credit: University of Colorado

In fluid dynamics, Airy wave theory (often referred to as linear wave theory) gives a linearised description of the …

Wave characteristics.

Dispersion of gravity waves on a fluid surface. Phase and group velocity divided by √(gh) as a function of h/λ. A: phase velocity, B: group velocity, C: phase and group velocity √(gh) valid in shallow water. Drawn lines: based on dispersion relation valid in arbitrary depth. Dashed lines: based on dispersion relation valid in deep water.

Orbital motion under linear waves. The yellow dots indicate the momentary position of fluid particles on their (orange) orbits. The black dots are the centres of the orbits.